Ford 8.8 Axle Swap
For S-10, from factory 10 bolt (7.5)

 

Introduction

Ok I'm going to start off with your typical disclaimer bullsh*t stuff here in saying that applications could vary, It's not my fault if you run into different problems or if you can't get it to fit, yadda, yadda, yadda. With that aside....

Why change rears in the first place? Well, if you have been around the S-10 scene or have a little background knowledge of the GM 10 bolts, you will know that the factory 7.5 and 7 5/8 rears are pretty unpredictable. There are guys out there who have run 10's, 11's, 12's on them with no problem then there's guys who didn't even make it off the starting line with a stock 350 snapping an axle or blowing the diff. Overall you could call it a pretty weak rearend unless you have upgraded axles, swapped the factory posi-loc for an eaton style, etc. and even then you still have a timebomb.

Personally I decided on the swap for a few reasons. #1, my truck came with an open diff and I couldn't pull any better than 2.4x 60' times at the track so the first thing I needed was a posi. Well after looking at my posi options and realizing how thin my wallet was, I had to come to a decision. I could either buy a factory style timebomb locker (G80 option) for $75-150, I could buy powertrax locker with unpredictable handling for $200-250, or I could dish out the dough on a quality eaton posi for $300-350. Now despite my worries of the posi's themselves I'm still using the puny 26 spline axles unless I want to dish out more on those and even then I still have a relatively small and weak rear end which I could risk breaking and wasting all the above invested money.

This is where I made my decision. I had heard a rumor that Ford Explorer rear ends were similar in width and were supposedly a good match to swap. This rear has a ring gear of 8.8 inches and is just as strong as a Chevy 12 bolt. They also have massive 1.32" diameter axles with 31 splines. On top of both all that, the limited slip rears only come in 3.55, 3.73, or 4:10 gears. All 3 are pretty awesome gears for street/strip. AND!! Last but not least, if you find one out of a '95+ Explorer it means they will have disc brakes, yes!! You can be upgrading strength, adding a posi, getting better gears, AND making a huge rear brake upgrade to discs all in one swap... can you imagine the money saved from doing that to your 10 bolt? Unfortunately there is next to zero resources out there rather than rumors on this swap, but with nothing to lose, I took some measurements of my stock 2wd rear from backing plate to backing plate (48") as well as the spring perch measurements (38.5"), and a copy of my bolt pattern and I headed off to the local junkyard. The first one I found was a '92 Explorer sitting on some tires. I took the measurements and found that the 8.8 rear was about 6 inches wider (3 inches per side) from backing plate to backing plate and 0.5" wider from spring perch to perch. Close enough for me!

I ran the numbers on the tag and found it to be equipped with 3.73 gears and a posi. I was given the price of $175 for the complete unit and all the connecting pieces including the sway bar and I jumped right on the deal.


*ADDED* Results may vary! I have had a few people talk to me and tell me that they have gotten different measurements on the width of the axle. I encourage everyone to go out and do measurements before they get involved or purchase the axle.

 



Here's the rear as I bought it. Drained fluid to check out the internals. As you can see it's a pretty massive unit.


This is the tag that you will want to check before you purchase the rear to find out what internals the rear has. You want to check the bottom left hand corner of the tag. It may be a little difficult to see, but in this instance you can see that it says 3L73 down there. The 373 is the gearing, so 3.73 obviously, and the L in the middle means that it is limited slip (posi). If it had a space where the L is and it just said 3 73 then it would mean it was an open carrier.




Here it is all cleaned up and painted. I first sprayed it down with purple castrol degreaser cleaner, then I used a wire brush attached to a drill as well as a bunch of steel wool and sandpaper to get it smooth and clean. Then I coated it with 3 or 4 coats of high durability paint.

 



Comparison of the old chevy 10 bolt 7.5 and the new 8.8. The flanges facing rearward are for the sway bar to attach to. If you're running heavy duty or thick shocks, you may need to trim the flange a little to allow shock mounting.



The pinion depth is actually the same on both rear ends which saves a huge driveline length headache



Here the diffs are lined up evenly to show the difference in width between the two. The 8.8 is overall 6 inches
wider, which gives it about 3 inches extra length per side. Not bad, and you can make it up in wheel backspacing.



One of the few changes you will need to make is for your Chevy driveshaft to mate to the Ford rear end. As you may have noticed, the Ford rear uses a disk style pinion yoke rather than the direct U-joint yoke. The problem is solved by getting the piece that mates to the disc yoke off of the driveshaft from the explorer. After that you will need to buy a new U-joint which has a set of internal and external ends (internal for the driveshaft, and external for the yoke). This U-Joint is part #372 from NAPA (Update: I was informed that NAPA may have changed the u-joint part # to #2400356) . You could also replace the entire rear pinion yoke with a piece sold by M.O.R.E.




Another area of concern was the brakes. I was relieved to find that it was simple to just use the factory S-10 brake line up to the splitter, and the lines that came with the rear threaded directly in.


The last problem I ran into (that I was already aware of) was the bolt pattern. I have both my street tires and slicks mounted on chevy rims so I didn't want to have to buy ford wheels. The rear is already as wide as I want to go so adapter plates were out of the question. I found a machine shop that would do the chevy lug coversion for $80. Also, unfortunately my rear was from a pre-'95 so it came with drum brakes. Never the less these ones stop better than my old ones did, and a disc upgrade would be cheap and easy.



Depending on the shocks you are using, you may need to trim this plate where the sway bar originally attached to the axle. I used just standard sized shocks so I had enough room so that it won't hit. If you want to use the sway bar then you will need to relocate the bottom shock mount which is a simple cut and weld.



Here it is sitting up in for test fitting. The spring perch location is approximately 0.5" wider than the 7.5, but there is no need for modification, I just yanked on the leaf spring a little and it popped right onto the stud.



Looks good in there doesn't it?



Gotta clean up the rest of the undercarriage now



Here's how far my tire sticks out now. This is with 3.5 backspacing though. If I jump it up to 4.5" or 5", you won't even see a difference. Makes it look a little more aggressive anyways.



Another profile shot

 


Stop looking at my rear! Goodbye old, hello new



Oh yeah! You can tell by the look on her face that she likes it

website-hit-counters.com
hit counter


Well that's it for now, if you have any questions feel free to e-mail me at knanthrup@comcast.net or you can find me on S10v8.com under the same nick name









And remember... safety first!!
Check out what happened when the strap on my transmission jack wasn't secure. The whole rear axle fell off and landed on my leg. It didn't break it but I got some nasty swelling and internal bleeding. Put me down for a few days.